Compositions for the stabilization of substances against the detrimental action of ultra-violet radiation



April 3, 1956 LOG 6' w. K. T. GLEIM 2,740,761 COMPOSITIONS FOR THESTABILIZATION OF SUBSTANCES AGAINST THE DETRIMENTAL ACTION OFULTRA-VIOLET RADIATION Filed Oct. 11, 1952 4-METHYL- COUMARIN f4-METHYL- 7- HYDROXY-COUMARIN 4-METHYL-6, 7DlHYDROXY-- COUMARIN MIXTUREOF 1 PT. 4METHYL,1PT. 4METHYL-7-HYDROXY-,

AND 3 PTS. 4-METHYL6,7DIHYDROXY COUMARIN yaw/M527 ATTOR NE 8'COMPOSITIQNS FUR THE STABHJHZATHGN. (BF SUBSTANCES AGAINST THEDETRHWHENTAL ACTION OF ULTRA-VIOLET RADEATKQN William K. r. Gleim,Grland rant, 1a., assignor to on.

versal Oil Products Company, Chicago, E11,, a corporation of Delaware 7Application ()ctober 11, 1952, Serial No. 314,340 11 Claims. or.252--300l ducing the harmful effects of ultra-violet radiations. 1 Morespecifically, the invention concerns the utilization of certainderivatives of coumarin as absorbentsof ultra-violet radiations within acertain range of Wave lengths generally considered to be primary factorsin deterioration of certain substances when exposed to sunlight.

It is well recognized that certain substances, particularly materialshaving an unstable or labile chemical structure, deteriorate uponexposure to sunlight which is composed of. radiations of all wavelengths in the ultra-violet portion of the spectrum. It is recognized,for example, that certain dyes in wearing apparel and other fabrics arebleached or converted to an undesirable color modification when thefabric is exposed to sunlight for prolonged, and in some cases, evenrelatively short periods ofexposure. It is a commonplace observation,too, that exposure of. the human skin to direct sunlight for suflicientperiods of time causes inflammation of the skin or sunburn. Further, itis known that certain valuable food accessory factors, such as vitamin Aand its precursors, the carotenes, are sensitive to ultra-violet lightand are made at least partially inelfective insofar as their foodaccessory values are concerned upon exposure of the food to direct oreven diffuse sunlight for extended periods of time It has now beendetermined that ultra-violet radiationsof only a certainlimited range ofwave lengths out of the total ultra-violet spectrum are responsible formany of the aforesaid undesirable effects of exposure tosunlight. Forexample, ultra-violet radiations of from 2800 toabout 3500 Angstromunits. of wave length cause infiammation of the human skin and thedesirable tanning ,efiect of sunlight is the result of the action ofultraviolet radiations of lower and higher Wave lengths thanthoseoffromabout 2800 to about 3500 Angstrom units. It

.is'anobject of this invention tosupply a composition of matter whichwill absorb ultra-violet radiations of undesirable wave lengths whenspread upon the-exposed surface of admixed with a material sensitive toultra-violet radiations or subject to deterioration when exposedthereto. z 1' In. one of its embodiments the present inventionconcerns acomposition of matter which diminishes the transrnission. ofultra-violet. light of wave lengths of from 2,740,751 Patented Apr-.3,19 56 marin.

Otherobjects and embodiments ofthe invention relating to specificaspects of the present composition of matter and to methods of applyingthe same-will be referred to in greater. detail in the following furtherdescription of the invention,

' The individual 4-rnethylcoumarin derivatives utilized in the presentcomposition as ultra-violet radiation screening agents absorb radiationshaving wave lengths throughout the range of from about 2,000-to about4,000 Angstrom. units and each exhibit maximum absorption at particularranges of wave lengths within the above range. 4-methylcoumarin, forexample, has a broadab- SOIpllOLL band of from about 2,500 to about3,200 Angstrom units and displays a maximum absorption of ultra-violetradiation having a. wave length of approximately 2,700 Angstrom units.The logarithm of the molecular extinctioncoefiicient, indicates thatless than 1% of ultra-violet radiations of 2,700 Angstrom. unitswavelength is. transmitted through a film 0.3 mm. thickofithe4-rnethylcoumarin contained in a solution of. approxi' 'mately 0.1%concentration, Designated in another manner, the logarithm of the molarextinction co-eflicient, that is, log 2, for radiations of 2,700Angstrom units wave length through a film of 4-methylcournarin' is equalto 4.19. 4-methyl-7-hydroxycoumarin absorbs ultra-violet radiations ofrelatively broadrange ofwave lengths, up about 3,500 Angstrom units anddisplays a maximum absorption or log =4.16 when the radiationsare of3,220 Angstrom units in wave length. 4-methyl-6,7-di-hydroxycoumarinabsorbs radiations over a still broader range of wave lengths, uptoabout 3900 Angstrom units and is particularly effective absorbent forultra-violet radiations of from 3,200 to 4,000 Angstrom units in wavelength. An ultra-violet absorption composition may, therefore, beprovidedwhich absorbs radiation of 2,700 Angstrom units most efficientlyand radiations of shorter or longer .wave lengths somewhat lessefficiently by coating the. surface exposed to the ultra-violetradiations with 4-methylcoumarin. Likewise, a mixture consisting of4-methylcoumarin and 4-methyl-7-hydroxycoumarin absorbs ultravioletradiations of from about 2,700 Angstrom units most 'eificiently (99%),while a mixture consisting of 4-methylcoumarin,4-methyl-7-hydroxycoumarin, and 4-methyl-6,7- di-hydroxycoumarin absorbsa large proportion of ultraviolet radiations over the entire range offrom about 2,000 to about 4,000 Angstrom units. Thus, although4-methylcoumarin absorbs ultra-violet radiations in the lower portion.of the range from 2,000 to 4,000 Angstrom units most effectively,preferred compositions which will be effective for screeningultra-violet radiations over the broader range of Wave lengths mustcontain an appreciable; quantity of the 4-methyl-7-hydroxycoumarin andthe 4-methyl-6,7- dihydroxycoumarin components, the latter componentsreducing the transmittance of ultra-violet radiation of higher .wavelengths in the upper portion of the range from 2,000 to 4,000 Angstromunits, generally considered to bathe more harmful wave lengthradiations. The results of ing amounts. of the individual4-methylcoumarin and 7- hydroxy and 6,7 dihydroxy derivatives of 4methylcoumarin indicate that compositions to be effective ultravioletscreening agents over the entire range of from about 2,000 to about4,000 Angstrom units, and particu larly of those radiations in the rangeof wave lengths from about 3,500 to about 3,800 Angstrom units, mustcontain at least 25% and preferably at least 30% by weight of themixture of 4-methyl-6,7-dihydroxycoumarin, at least 5% by weight of themixture of components of 4-methylcoumarin, and at least 20% by weight ofthe mixture of 4-methyl-7-hydroxycournarin. The proportion of 7-hydroxyand 6,7-dihydroxy derivatives of 4-methylcoumarin in the composition maybe varied and the effective quantitles of each inthe composition aremutually dependent within the above minimum limitations; however, whenthe proportion of the 4-methyl-6,7-dihydroxycoumarin derivative in thecomposition is reduced to below 30% by weight of the mixture, theproportion of the 4-methyl-7- hydroxycoumarin component must beincreased substantially in order for the resulting mixture to reduce thetransmittance of ultra-violet radiations at least 99% (or 1%transmittance). Thus, an ultra-violet screening composition containingonly 25% by weight of the 4-methyl-6,7- dihydroxycoumarin component inthe mixture, must contain approximately 70% by weight of the4-methyl-7-hydroxycoumarin component to be sufiiciently effective toreduce-99% transmittance of radiations from 2,000 to 4,000 m. wavelengths. of 5% by weight of the 4-rnethyl-6,7-dihydroxycoumarincomponent in the mixture, that is, to a total proportion of 30% byweight of the mixture, reduces the required amount of4-methyl-7-hydroxycoumarin to about 40% by weight of the total mixture,the remaining 30% being the less costly 4-methyl-coumarin component. Itis to be emphasized that the indicated proportions of the4-methylcoumarin and its 7-hydroxy and 6,7-dihydroxy derivatives areintended to provide at least 99% absorption of ultraviolet radiations inthe indicated range of wave lengths based on a composition containing 1%by weight of the indicated mixture of coumarin derivatives, anabsorption standard considered as effective for the intended purposes ofthe ultra-violet screening composition. A particularly preferred mixtureof said 4-methylcoumarin and the indicated derivatives thereof consistsof approximately one part by weight each of 4-methyl-, and 4-methyl-7-hydroxycoumarin and three parts by weight of 4-methyl-6,7-di-hydroxycoumarin, said mixture absorbing ultraviolet radiationsuniforrnly from about 2,000 to about 3,900 A., and particularly fromabout 2,500 to about 3,800.

A mixture of coumarin derivatives containing the above quantities ofeach derivative provides an effective screenagent of ultra-violet lightradiations within the indicated range of wave lengths and when appliedto the surface of a material sensitive to ultra-violet radiations, thecomposition excludes that portion of the ultra-violet spectrumconsidered to be detrimental.

In utilizing the above indicated coumarin derivatives as ultra-violetlight screening agents in any particular application or usage thereof,the mixture of coumarin derivatives is desirably mixed with a convenientvehicle for application to the surface of the material to be protectedfrom ultra-violet radiations or mixed with or impregnated in thematerial intended to be protected. One use of the present composition isthe preservation of the carotene content of forage crops after cuttingand during thecuring stage to which the crop is normally subjectedbefore feeding. In these curing operations, the crop, such as alfalfa,after mowing is allowed to lie exposed to the elements, includingsunshine, for from several days to several weeks during the curingprocess. Test observations during the curing interval when the foragecrop is exposed to the ultra-violet radiations present in sunlight, haveshown that the cerotene normally present in relatively high quantitiesin alfalfa when freshly cut and which is ultimately converted to vitaminA during the digestion of the forage crop by the particular animal Onthe other hand, an increase consuming the same, is rapidly destroyed asthe curing operation begins and is ultimately reduced substantially tonil at the end of the period required for storage and curing. Thevaluable carotene content of such forage crops, however, may bepreserved to a value representing substantially its original content inthe forage crop at the time the same is cut by applying the presentultraviolet absorbing agent to the forage crop immediately prior tocutting or immediately following cutting and prior to the curing stage.I

The present ultra-violet light screening agents consisting of a mixtureof the various coumarin derivatives indicated above, may be sprayed onthe forage crop'in the form-of a solution of the ultra-violet lightscreening agent in a suitable solvent, such as dilute ethanol. Thecomposition may also be emulsified in Water with the aid of a detergentor other surface active agent to promote emulsification or suspended ina non-polar suspending medium with the aid of non-ionic detergents andthe resulting emulsion applied to the forage crop. The ultra-violetlight screening agents are effective in very low concentrations withinthe suspending medium such that large fields of forage crops may besprayed economical y, as for example, with various machine-type sprayersor by spraying the composition on the forage crop from an airplaneflying over the field. For large scale operation,

as, for example, for the purpose of spraying forage crops, 7

often as little as 0.01% byweight of the indicated 7 coumarincomponents. I

Another typical use of the present ultra-violet light screening agent isits application as an absorbent of harmful ultra-violet radiations: fromsunlight for suntanning purposes. The mixture of coumarins for such usemay be dissolved in alcohol or suspended in lanolin or Vaseline toprovide a suitable ointment which may be applied to the surface of theskin for the prevention of sunburn. Suitable ointment or lotioncompositions may contain the mixture of coumarin derivatives amounts offrom about 0.1% to about 5% by weight of the ultimate ointment or lotioncomposition.

vFabrics may be protected from the bleaching action of sunlight byimpregnating the fibres of the fabric with a solution or emulsion of thecoumarin derivatives, or ultra-violet light screening agent compositionherein provided and thereafter allowing the suspending agent or solventof the coumarin to evaporate, depositing a residue of the coumarinderivatives in the innermost portions of the fibre and in contact withthe dye subject to the bleaching action of the sunlight.

Another method to protect fabrics and also to protect foods or othersubstances whose flavor, color, or other in which the light-sensitivematerial is contained, may,

have their surface coated with a thin layer of the mixture of coumarins,or the mixture of coumarin derivatives may be incorporated into thematerial from which the containers are manufactured by impregnating thecontainer with a solution or emulsion of the coumarin derivatives. Whenthe container is fabricated from waxed paper, as, for example, for thepreparation of. bags for potato chips which are peculiarly subject torancidification by virtue of the action of ultra-violet light upon thefat contained in the potato chips in the presence of atmospheric oxygen,the wax utilized for impregnating the paper may contain the presentcoumarin derivatives prior to the impregnation treatment and thusdeposit the ultra-violet screening agent in the fibrous structure of thebag, thereby preventing the entry of ultra-violet radiations into thebag in contact with the light-sensitive contents thereof.

In any of the above mentioned methods of applying the presentultra-violet light screening agents, or in any other method of applyingthe same, the material to be protected from the action of ultra-violetlight radiations is applied to the surface of the object or the fibroujsstructureof the material is impregnated with the screening agent. Manyadditional and varied uses of the present mixture of coumarinderivatives as light screening agents are readily apparent to thoseskilled in the art and such uses may be devised as the need for lightprotecting agents arises.

The present composition comprising amixture of the indicated coumarinderivatives may also. containother components which enhance theultra-violet light screening effect of the indicated coumarins orachieve an incidental effect consistent with the particular applicationof the present composition. Thus, the composition may containincorporated therewith. a substance havingv the capacity of deactivatingthe catalytic effect of metallic impurities, such as iron, copper,nickel, etc., salts or oxides which normally-would enhance the oxidationor rancidification of food products or other materials in contacttherewith. Other substances, for example, which may be incorporatedwith. the present. coumarin ultra violetlight screening agents arespecific organic compoundswhichact as oxidation inhibitors andv whichlikewise havethe eifect of reducing the tendency of food products orother mateparticularly useful in coating food packaging materials areselected from a group of compounds characterized as2-tert-alkyl-4-alkoxyphenols, one of the preferred inhibitors of thisgroup comprising 2-tert-butyl-4-methoxyphenol. Suitable compositionscontaining an oxidation inhibitor, a light screening agent comprisingthe present mixture of coumarin derivatives and a carrying medium forthe above components may contain, for example, from about 0.1 to about5% by weight of the mixed coumarin derivatives, from about 0.1 to about2.0% of the oxidation inhibitor, such as 2-tert-butyl-4-methoxyphenol,and the remainder, a suitable carrier or solvent of the above componentssuch as an animal vegetable or petroleum Wax. For the purposes ofcoating packaging materials other than for food containers, variousother inhibitors, which may be toxic or non-toxic, may be utilized inthe coating composition. Compounds of the cresol, butylphenol,phenylenediamine, and aminophenol type, as Well as nordihydroquaiareticacid, propylgallate 2,4-dimethyl- 6-tert. butylphenol, 2,6-ditertbutyl-4-methylphenol, 2,2- dimethyl-6-tertbutyl-5-hydroxycoumarin, etc.may be utilized in the coating composition as oxidation inhibitors,especially when the packaging container is to be utilized for enclosingmaterials other than food and where the toxic properties of theinhibitor is not an important factor in the choice of a component forthe particular application.

This invention is further described with reference to light screeningproperties of the specific coumarin derivatives employed in the presentcomposition in the following examples.

EXAMPLE I Known solutions of 4-methylcoumarin, 4-methyl-7-hydroxy-coumarin, 4-methyl-6,7-dihydroxy-coumarin and a known solutionof a mixture of 1 part by weight of the 4-methyl-, 1 part by weight ofthe 4-methyl-7-hydroxy-, and 3 parts by weight of the4-methyl-6,7-dihydroxycoumarin derivatives in 95% alcohol were preparedand placed in an ultra-violet absorption spectrophotometer to obtain themolar extinction coefiicients for the respec- 6 tivesamples. Theresulting absorption spectra are reproduced in the accompanying diagram.The absorption spectrogram curves indicate that less than 1%transmission of ultra-violet light occurs at concentrations of fromabout 0.1% to 1.0% by weight of the light screening agent through alayer of 0.3 mm. in thickness.

Although the specific mixture of the present light screening coumarinderivatives operates efiici'ently to exelude ultra-violet radiationsover the broad range indicated (from about2500 to about 3900 A.), othermixtures maybe compounded to absorb efilciently' over a still broaderrange or to absorb within a more limited range of ultra-violet wavelengths, to serve the particular purposes desired.

. EXAMPLE II Known solutions of a-series of ultra-violet screeningcompositions containing various proportions of 4-methylcoumarin,4methyl-7 hydroxycoumarin and 4-methyl-6,7- dihydroxycoumarin weretester in an ultra-violet absorption spectrophotometer to determinetheabsorbance value for each of the compositions. The following'Table'Ipresents the absorbances for each composition spread to a thickness of0.3 mm., the latter thickness being consid'ered'the usual amount ofcomposition which would be applied'to the surface of an object orsubstance subject to ultra-violet radiations in ordinary usage.

Table I [Absorbancm Agg g g' for ultra-violet radiations of mixtures 014-naethylcoumarin, 4 methyl-7-hydroxycoumariu and 4-methyl-6,7-dihydroxycoumarlm] 'NOTE.C1 is 4-methylcoumariu; C5 is 4methyl-7-hydroxycoumariu; C; is 4-methyl-6,7-dihydroxy-coumarin.

It will be noted from the results presented inthe above Table I that inorder to have an absorbance of at least 2 (that is, less than 1%transmission of ultra-violet radiation through a film of the appliedmixture, where absorbance is defined as the logarithm of the ratio ofthe intensity of light transmitted through a film of zero thickness tothe intensity of light through a film of a given thickness, which isequal to the logarithm of l/Transrnittance or the logarithm of 100,equal to 2) the composition at 1% concentration of the mixture in anorganic solvent must contain at least 25% by weight of4-methyl-6,7-dihydroxycoumarin, at least 5% by Weight of4-methyl-coumarin and at least 20% by weight of4-rnethyl-7-hydroxycoumarin. Suitable ratios of the quantities ofcoumarin derivatives in the ultra-violet screening composition are: fromabout 25% to about 75% by weight of 4-methyl-6,7-dil1ydroxycoumarin,from about 20 to about 70% by weight of 4-methyl-7-hydroxycoumarin, andfrom 5% to about 55% by weight of 4-methylcoumarin, although thepreferred ratios of each of the components is approximately equimolarproportions, or about 30.2 Weight percent of 4-methyl-coumarin, 33.3%4-methyl-7-hydroxycoumarin and about 36.5% by weight of4-methyl-6,7-dihydroxycoumarin.

I claim as my invention:

1. An ultra-violet light screening composition comprising a mixture ofat least 5% by weight of 4-methylcoumarin, at least 20% by weight of4-methyl-7-hydroxycoumarin, and at least 25% by weight of 4-methyl-6,7-dihydroxycoumarin.

2. The composition of claim 1 further characterized in that said mixturecontains from about 5 to about 55% by weight of 4-methylcoumarin, fromabout 20 to about 70% by weight of 4-methyl-7-hydroxycoumarin, and fromabout 25 to about 75% by weight of 4-methyl-6,7- dihydroxycoumarin.

3. The composition of claim 1 further characterized in that saidcomposition contains about 1% by weight of said mixture.

4. The composition of claim 1 further characterized in that saidcomposition comprises a mixture of cquimolar proportions of4-methylcoumarin, 4-methyl-7-hydroxy' coumarin and4-methyl-6,7-dihydroxycoumarin.

5. An ultra-violet light screening composition com prising a mixture ofabout one part by weight of 4-methylcoumarin, about one part by weightof 4'rnethyl-7-hydroxycoumarin, and about three parts by weight of4-methyl-6,7-dihydroxycournarin.

6. An ultra-violet light screening composition for wax paper containerscomprising a mixture of about one part by weight of 4-1nethylcoumarin,about one part by weight of 4-methyl-7-hydroxycoumarin, and about threeparts by weight of 4-methyl-6,7-dihydroxycoumarin and a wax dissolved insaid mixture.

7. The composition of claim 6 further characterized in that saidcomposition contains from about 0.01 to about 5 percent by weight ofsaid mixture of compounds.

8. An ultra-violet light screening composition comprising a fatoxidation inhibitor and a mixture of at least 5% by weight of4-methylcoumarin, at least 20% by 8 weight of4-methyl-7-hydroxycoumarin, at least 25% by weight of4-methyl-6,7-dihydroxycoumarin. 9. The composition of claim 8 furthercharacterized in that said oxidation inhibitor is a2-tcrt-alkyl-4-alkoxy phenol.

'10. An ultra-violet light screening composition comv prising a metaldeactivator and a mixture of at least 5%.

by weight of 4-methylcoumarin, at least by weight of4-methyl-7-hydroxycoumarin, at least by weight of4-methyl-6,7-dihydroxycoumarin.

11. An ultra-violet light screening composition comprising a metaldeactivator, a fat oxidation inhibitor and a mixture of at least 5% byweight of 4-methylcoumarin, at least 20% by weight of4-methyl-7-hydroxycoumarin, at least 25 by weight of4-methyl-6,7-dihydroxycoumarin;

References Cited in the file of this patent UNITED STATES PATENTS2,038,114 Joseph Apr. 21, 1936 2,279,468 Lahousse Apr. 14, 19422,528,769 McCracken Nov. 7, 1950 FOREIGN PATENTS 464,732 Great BritainApr. 23, 1937 OTHER REFERENCES The Am. Perfumer & Essential Oil Review,Sept. 1950, pp. 197-201 incl.

1. AN ULTRA-VIOLET LIGHT SCREENING COMPOSITION COMPRISING A MIXTURE OFAT LEAST 5% BY WEIGHT OF 4-METHYLCOUMARIN, AT LEAST 20% BY WEIGHT OF4-METHYL-7-HYDROXYCOUMARIN, AND AT LEAST 25% BY WEIGHT OF4-METHYL-6,7DIHYDROXYCOUMARIN.